1. Field of the Invention:
This invention relates to a magnetic recording apparatus having a plurality of magnetic heads mounted on a rotary drum.
2. Description of the Related Art:
The known apparatuses of the above-stated kind include video tape recorders (hereinafter referred to as VTR's). Recently, the size of VTR's has been reduced to a great extent. The helical scanning type VTR's of the so-called VHS type and .beta. type have been commercialized in varied forms including a portable tape deck and a VTR combined in one body with a camera. Further, the so-called 8 mm VTR's using a tape measuring 8 mm in width have been also commercialized. In the case of the 8 mm VTR, the rotary drum measures only about 40 mm. Some of the commercialized 8 mm VTR's are capable of recording and reproducing at a track pitch which is 1/2 of the ordinary track pitch.
In carrying out recording or reproduction with a VTR, the tape can be allowed to travel at varied speeds including a standard speed and a speed half of the standard speed. The half tape speed is used for increasing the recordable amount of the tape by two times. However, if two heads are arranged for recording or reproduction at the half tape speed in addition to two heads provided for recording or reproduction at the standard tape speed, the VTR must be provided with a rotary transformer of four channels.
In the case where the VTR includes a magnetic head for special reproduction purpose, a flying magnetic erasing head (hereinafter referred to as FEH) and the like, in addition to two recording/reproducing heads, a multi-channel rotary transformer is required. With the diameter of the rotary drum becoming smaller, the diameter of the rotary transformer also becomes smaller. Then, in accordance with the arrangement of the conventional VTR, it is difficult to reduce the cross-talk which takes place among the channels of the rotary transformer. The cross-talk takes place during both recording and reproduction. Assuming that a recording operation is performed with four heads arranged as mentioned above, for example, at the standard tape speed, some portion of the recording signal current to be supplied to the heads for the standard tape speed flows also to the heads provided for the half tape speed. In the event of excessive cross-talk, the recording signals would be degraded thereby. Particularly, in the case where a signal recorded on a tape is to be erased, by using the above-mentioned FEH, it is required to supply an erasing current, which is larger than the recording current, to the FEH, and consequently more cross-talk tends to take place through the rotary transformer.
In the case of the 8 mm VTR, a PCM (signal recording) area is prescribed to be provided on a magnetic recording medium apart from a video (signal recording) area for recording and reproduction of a digital audio signal which is time compressed and obtained by pulse-code modulating an audio signal. During recording, while one head is recording the signal in the PCM area, another head records a video signal in the video area at the same time. In the event of excessive cross-talk of the rotary transformer, the quality of record is degraded both in the picture and the sound as the recording video and PCM audio signals are affected by the cross-talk.